ALBERT

Description: Mechanical models to describe the slip behavior and displacement accumulation pattern of shallow slip on major fault zones are contradictory. Recent observations suggest that, despite low confining pressure and phyllosilicate rich fault gouges at shallow crustal levels, faults can surface. These recent observations necessitate a reinvestigation of the asperity and seismogenic zone model. The observation of triggered shallow slip events on segments of the Atacama Fault System (AFS) in N-Chile (Victor et al. that the AFS exhibits the ability to slip seismically at shallow depth. Our follow-up study now uses the IPOC Creepmeter Array to further investigate these slip events both from their instrumentally observed properties as well as their fault zone properties in the field, to unravel the spectrum of fault slip modes. 90 Lower Cruat Thicknessim: ' FC-‘JÜ “5:130 ' 5WD E4|3|30 ' 3'330 52'530 ‘ 1C'EI] Claromm Bmin 5}. V0w2», Colorado Bann 603:") Ü äÜCIJÜ 1330W 119530 206'305 256000 3mm 350030 400300 Eüürdlnate 5y51em' lJTl'."I 215 References J.‚ Wenderoth, H.—198—210. Claromecö. Exploracion 217—231. Back—Projection: Veral'z, F. Tilmannl'z, J. Saul1 — information related to the rupture area, rupture velocity, any prior fault geometry knowledge requirements. Its Iie Signals monitoring〉 Iimited description of high-frequency ruptures and is suitable to reaI-2007 Mw 7.7 Tocopilla earthquake located in the southern within their context. We found the high-frequency O.5-alonrg〉 welI as a barrier in this region. The method has offered an improvement in terms of resolution and data availability Ievels Victorl, Mütingl, Gonzalezl, Ievels, exhibit velocity weakening behavior all the way to the ofthe oftriggered ofthe aI. 2018) monitored with the IPOC Creepemter Array demonstrated seismicaIIy foIIow-weII ABSTRACTS of 8 years at 11 monitoring sites and comprises both triggered shallow slip events and creep signals. The recorded shallow slip events range from m to mm scale. Slip velocities for these events range between 10-11 -10-5 m/sec and slip durations up to 300 sec, therefore covering a spectrum from creep events to slow earthquakes. Further decomposing the time series recorded at the creepmeter stations we are able to differentiate between slow creeping fault segments and others which are accumulating displacement solely by triggered shallow that only one of the fault segments preferentially creeps at shallow depth, whereas the others preferentially accumulate permanent displacement by accumulation of series of one fault we see a transient creep signal of 1,5 years after an unusual rainfall event, which can be clearly discriminated from the otherwise not creeping signal. Comparing these observations with the fault gouge thickness at the creepmeter sites, we find a strong correlation the monitoring site and creeping fault behavior. By contrast fault segments, accumulating displacement only via developed. Instead these fault contacts are developed in a strongly fragmented basement/basement contact zone or show a submillimeter thin sharp contact in alluvial fan sediment. These first results demonstrate that AFS fault segments at shallow depth exhibit a spectrum of that is closely linked to fault zone properties, therefore corroborating the ability of seismic rupture potential at shallow crustal levels.